The continuous shrinking in dimensions of electronic devices utilized in ULSI circuits in recent years has resulted in increasing the resistance of the BEOL metallization as well as increasing the capacitance of the intralayer and interlayer. This combined effect increases signal delays in ULSI electronic devices. In order to improve the switching performance of future ULSI circuits, low dielectric constant (k) insulators and particularly those with k significantly lower than that of silicon oxide are needed to reduce the capacitances. Dielectric materials that have low k values have been commercially available, for instance, one of such materials is polytetrafluoroethylene (PTFE) with a k value of 2.0. However, these dielectric materials are not thermally stable when exposed to temperatures above 300.about.350.degree. C. which renders them useless during integration of these dielectrics in ULSI chips which require a thermal stability of at least 400.degree. C.
The low-k materials that have been considered for applications in ULSI devices include polymers containing Si, C, O, such as methylsiloxane, methylsesquioxanes, and other organic and inorganic polymers. For instance, materials described in a paper "Properties of new low dielectric constant spin-on silicon oxide based dielectrics" by N.Hacker et al., published in Mat. Res. Soc. Symp. Proc., vol. 476 (1997) p25 appear to satisfy the thermal stability requirement, even though some of these materials propagate cracks easily when reaching thicknesses needed for integration in the interconnect structure when films are prepared by a spin-on technique. Furthermore, the precursor materials are high cost and prohibitive for use in mass production. In contrast to this, most of the fabrication steps of VLSI and ULSI chips are carried out by plasma enhanced chemical or physical vapor deposition techniques. The ability to fabricate a low-k material by a PECVD technique using readily available processing equipment will thus simplify its integration in the manufacturing process, reduce manufacturing cost, and create less hazardous waste. A application (Ser. No. 09/107,567), now U.S. Pat. No. 6,147,009, assigned to the common assignee of the present invention, which is incorporated here by reference in its entirety, described a low dielectric constant material consisting of Si, C, O and H atoms having a dielectric constant not more than 3.6 and which exhibits very low crack propagation velocities. Further reduction of the dielectric constant of such a material will further improve the performance of electronic devices incorporating such dielectric.
It is therefore an object of the present invention to provide a low dielectric constant material consisting of two or more phases and having a dielectric constant of not more than 3.2.
It is another object of the present invention to provide methods for fabricating the multiphase materials of this invention.
It is a further object of the present invention to provide a method for fabricating a multiphase material wherein the first phase is a hydrogenated oxidized silicon carbon film (contains Si, C, O and H and henceforth called SiCOH), and at least a second phase consisting essentially of C and H atoms.
It is a further object of the present invention to prepare a multiphase material that contains nanometer-sized voids.
It is another further object of the present invention to prepare a multiphase material that has a dielectric constant which is at least 10% lower than that of a single phase SiCOH dielectric material.
It is another further object of the present invention to provide a method for fabricating a low dielectric constant, thermally stable multiphase film from a precursor mixture which contains two or more different precursor molecules.
It is still another further object of the present invention to provide a method for fabricating a low dielectric constant material including two or more phases in a parallel plate plasma enhanced chemical vapor deposition chamber.
It is still another further object of the present invention to provide a method for fabricating a low dielectric constant material including two or more phases using a remote plasma chemical vapor deposition process.
It is yet another object of the present invention to provide a method for fabricating a multiphase material for use in electronic structures as an intralevel or interlevel dielectric in a BEOL interconnect structure.
It is yet another further object of the present invention to provide a multiphase material with a low internal stress and a dielectric constant of not higher than 3.2.
It is still another further object of the present invention to provide an electronic structure incorporating layers of insulating materials as intralevel or interlevel dielectrics in a BEOL wiring structure in which at least one of the layers of insulating materials is a multiphase material.
It is yet another further object of the present invention to provide an electronic structure which has layers of multiphase materials as intralevel or interlevel dielectrics in a BEOL wiring structure which contains at least one dielectric cap layer formed of different materials for use as a reactive ion etching mask, a polish stop or a diffusion barrier.